Question 174116
"I am 3 times as old as Sue is'" Frank said to Ann. "On the other hand, I am 15 years older than John, while Sue is 1 year ow old am I?"

If x = John's age,

x - 1 = Sue's age

x + 15 = Frank's age

3(x - 1) = Frank's age also 

Just use the two expressions I have set up for Frank and solve for John's age (x).

3(x - 1) = x + 15

Can you take it from here?